In many food processing operations, pieces of foods are produced that are regarded as being less valuable than other, typically larger pieces. Further, some food pieces can be produced that are less valuable than others, simply as a result of their qualities, e.g. some cuts of meat are less desirable than others because they are too tough.
A number of methods have been developed to produce reconstituted food products from such lower value food pieces, where the reconstituted food products have sizes and properties that make them more valuable than the lower value food pieces. Reconstitution is typically achieved by comminuting the food pieces and combining them with additives that will bind them together. The methods and recipes for producing reconstituted food products vary greatly, but typical examples are corned beef, sausages, and the like.
While existing methods of preparing reconstituted food products generally do not attempt to provide such a product, it would be greatly beneficial if a reconstitution process can provide a food product that resembles an unprocessed high value food product, e.g. if lower value cuts of meat, off-cuts, etc. can be processed to provide a food product that resembles a whole muscle of preferred cut of high quality meat.
Processes have been proposed for preparing such a reconstituted food product, e.g. in International Patent Application No. WO 2004/008876 (to Melnyczuk), the content of which is included herein in its entirety, by reference. However, existing food processing equipment and techniques are prone to a number of deficiencies which make them unsuitable for the preparation of a reconstituted food product as described above. In order to prepare a reconstituted food product as described above from food pieces, the pieces need to be combined with additives to bind them and to impart other desired characteristics to them, such as consistency and texture. These additives need to be evenly distributed in the process stream of food pieces to impart these characteristics evenly and this should be done before the additives react to bind the food pieces. Further, in order to provide a reconstituted food product that resembles a whole, high quality product, the food pieces also need to be processed to homogenise them while maintaining their structure and texture, produce a desired grain structure, etc. It has been proposed in WO 2004/008876 that this be done in a static mixer, but none of the prior art static mixers are particularly suitable for mixing these food pieces and additives, especially where the food pieces include elongate fibres or strands that have a tendency to catch on food processing equipment.
The term “static mixers” refers to a wide variety of devices that usually comprise an insert that is placed inside a tube through which a liquid, gel, paste or the like, flows. The purpose of the insert is typically to mix the flowing material to homogenise it, although it can also serve ancillary purposes such as agitation, comminution, etc.
Examples of static mixers of this type, are disclosed in U.S. Pat. Nos. 5,425,581 (to Palm) and 7,040,802 (to Füglister), which include mixer inserts that are received inside cylindrical tubes. However, when mixers are used in applications where they need to be cleaned regularly, such as in the food processing industry, and where aggressive mixing is required, such as in the processing of meat products, these configurations are not ideal, since the intricate geometries of the inserts make them difficult and/or costly to clean regularly, even when they have been removed from the cylindrical tubes.
An improved static mixer has been disclosed in WO 2004/008876, in which the elements that cause the mixing are in the form of blades that are fixedly attached to walling elements and the walling elements are positioned side-by-side to form the tube through which the material flows. This improvement allows the mixer to be disassembled very easily to a state in which its components can be cleaned easily and effectively. However, this mixer holds the disadvantages that the flow of material immediately downstream of the blades tends to stagnate in some instances and in some instances, inadequate mixing occurs largely because some of the material can pass between the blades along a three dimensional zigzag-like passage, rather than being adequately folded within the mixer.
Other deficiencies of existing food processing equipment relate to an inability to ensure even distribution of the additives in the food pieces in a continuous process that can be stopped and re-started relatively easily. The result of uneven distribution of additives is that some parts of the reconstituted food product will receive too much additive and thus set too firmly, while other parts will receive an insufficient dosage of one or more additives and thus either remain too soft, or not set at all. Preferably, the setting of food product inside processing equipment when the process is stopped, should be avoided or kept to a minimum, since the set or partially set food product will either need to be removed before the process can be re-started, or will disrupt product consistency.
Some methods of preparing reconstituted food products are carried out in batches in which the additives are added to the food pieces and they are thoroughly mixed and processed, e.g. as described in U.S. Pat. No. 4,603,054. However, the entire batch of the food pieces is brought into contact with the additives at the same time, which causes setting to begin, but the batch is processed further over a length of time and the degree of setting that has taken place in food pieces when they proceed to further processing varies.
One way to address this problem is by keeping batch sizes small so that the batch can be processed relatively promptly to minimise the variance during the course of processing, in the degree of setting that takes place. Production in small batches, in which the equipment has to be cleared of partially or fully set reconstituted product after each batch, is not cost effective.
Another way of addressing this problem is to add buffering agents to the food mixture to delay setting, e.g. to provide a typical window period of twelve hours. However, the use of buffering agents may require larger quantities of setting agents in the mixture, which could lead to secondary sineresis, especially if there is incorrect or inadequate mixing. During the window period, the mixture needs to be stored, which requires additional handling and storage facilities, which typically needs to be refrigerated. The likelihood of contamination of the food product is also typically increased during the additional handling and storage.
Continuous methods can be used for the production of reconstituted food products and examples of existing methods are provided in U.S. Pat. No. 5,783,241 and in WO 2004/008876, in which the gelling agents and setting agents are added to a product stream. However, as mentioned above, unless a buffering agent is used, setting commences as soon as the gelling agent and setting agent come into contact with each other and in existing processes, this occurs at some stage before the food product stream is finally processed. In particular, in WO 2004/008876, the additives are added to the process stream together, upstream of the static mixer and setting commences before the product stream is processed in the mixer. This has two disadvantages, the first being that it causes excessive setting of the product before or during mixing, that increases the energy requirement of the mixing process and reduces the effectiveness of the mixing process. The second disadvantage is that, in the event of a process stoppage, the mixture of gelling agent, setting agent and food pieces upstream of the static mixer will set and will need to be removed before the process can be re-started.
In some instances, especially if food pieces in the form of relatively tough meat is used, it is preferable to pre-treat the food pieces in a tenderiser, in order to increase the surface area of the food pieces that is exposed to additives and thus improve cohesion during setting, to reduce the size of inconsistencies in the food pieces, to provide a more natural looking grain, to achieve desired tenderness characteristics, to impart a texture to the food pieces that makes them more workable in the reconstitution process, and the like. However, existing tenderisers have been found not to perform adequately.
Existing methods of tenderising foods typically include percussive methods such as pounding with a mallet, penetrating methods in which needles or blades penetrate the food and tenderisers passing foods through counter rotating rollers or gears, such as that disclosed in European Patent No. EP 0930015 (to Bonon et al). Percussive tenderising is too time consuming to be used effectively on an industrial scale and penetrating methods of tenderising are not sufficiently effective in flattening food pieces while maintaining its fibre structure largely intact, as is preferable in pre-treatment for reconstitution of a food product, as described above. It is often difficult to control or adjust the extent of tenderisation in some roller/gear type tenderisers, with the result that the tenderised food pieces often lack the desired consistency and/or texture.
The tenderiser of EP 0930015 would impart most of the required characteristics to the food pieces, but has a number of disadvantages for use in pre-treatment of food pieces before reconstitution. In particular, food pieces are often not pulled into the gap between the rollers and simply roll around on top of the rollers. The use of this type of tenderiser also requires preparation of the food pieces before tenderising, e.g. by slicing the food in a particular way, that is cumbersome and/or costly. Further, the tenderiser of EP 0930015 is not well suited to tenderising pre-frozen meat, which can be very inhibiting since many bulk manufacturers prefer to use meat that can be sourced and stored frozen.
The reason for the unsuitability of the EP 0930015 tenderiser results largely from the dehydration of meat during freezing and defrosting, which causes the meat surface to be watery, resulting in meat pieces that are slippery and often do not pass through the rollers, but slide around on top of the rollers. Further, if a vacuum filler is used, the removal of unbound water from the defrosted meat causes a loss in mass and thus value and causes a loss in the lubricating effect of the moisture, thus making the meat pieces difficult to pump. A water binder can be added to the meat to compensate for the loss of lubrication and for ease of processing (relating to distribution of the gel and reduction of meat handling). This should preferably be done before the meat is tenderised, but the water binder causes the meat surfaces to be even more slippery and exacerbates the problem of meat pieces sliding around on top of the rollers. Further, the addition of a water binder causes the meat to stick to the rollers after the tenderisation and not to be removed entirely by the scrapers, especially in the event that the rollers have surface features on them (e.g. ridges, grooves or teeth). It is preferable that slices of meat are fed into the EP 0930015 tenderiser, rather than cubes, but it is difficult to cover slices evenly with a water binder.
The EP 0930015 tenderiser is also unsuitable for use in reconstitution, since it cannot be used for tenderising meat with a wide variety of characteristics, as is often the case in the typical supplies of meat for reconstitution. The tenderiser itself is large, but the process is slow, since only a few pieces of meat can be fed through at a time.
The present invention seeks to provide for the manufacturing of reconstituted food products, overcoming the drawbacks in the prior art. In particular, the present invention seeks to provide a static mixer that can impart adequate mixing to the material flowing through the mixer, while adequately maintaining the structure and texture of the material and that can be cleaned with relative ease and efficiency. The present invention also seeks to provide for continuous dosing, mixing, shaping and setting at a constant speed to provide a reconstituted food product with a consistent texture and cohesion, even if the manufacturing process is interrupted from time to time. The present invention further seeks to provide for tenderising of food pieces, prior to manufacturing of reconstituted food products.